Recruitment in Tropical Tree Species: Revealing Complex Spatial Patterns

Seed dispersal should leave a signature on the spatial distribution of recruits that can be quantified using sophisticated techniques of spatial pattern analysis. Here we study spatial patterns of five frugivore-dispersed tropical tree species at the Barro Colorado Island forest, Panama, to describe detailed properties of the spatial patterns of recruits and to investigate whether these patterns were produced by temporally consistent mechanisms. Our spatial point pattern analyses detected the existence of surprising spatial structures, such as double-cluster and superposition patterns, and they allowed for a detailed quantification of their properties. The spatial recruitment patterns were composed of two independent components comprising a random component and a component showing a complex spatial pattern with two critical scales of clustering. The analysis allowed an estimation of the relative contribution of scatter dispersal versus clump dispersal in effective seed dispersal for our study species. Additionally, the cluster characteristics were temporally consistent over 25 years and correlated with several species traits. We are just beginning to discover the richness of spatial patterns found at tropical forests, and we are confident that a combination of advanced point pattern analysis with field data will allow for significant advances in establishing the link between spatial patterns and processes.